GB2298260A

GB2298260A - Vibration-damping link

Info

Publication number: GB2298260A
Application number: GB9503631A
Authority: GB
Inventors: Ludovic Chauvet; Patrice Fort; Serge Vassiliadis
Original assignee: Draftex Industries Ltd
Current assignee: Laird Holdings Ltd
Priority date: 1995-02-23
Filing date: 1995-02-23
Publication date: 1996-08-28
Anticipated expiration: 2015-02-23
Also published as: GB9503631D0; ES2140626T3; DE69514641T2; EP0728959B1; EP0728959A1; DE69514641D1; GB2298260B

Description

2298260 1 VIBRATION-DAMPING LIN The invention relates to vibration-damping

links. Embodiments of the invention to be described in more detail below are in the form of vibration-damping links or "torque links" used for vibration damping in motor vehicles. For example, such a link may be used as part of the support system for supporting the engine of the vehicle from the body or chassis of the vehicle in a manner which damps the vibrations of the engine and minimises their transmission to the chassis or body.

According to the invention, there is provided a v i brat ion-damping link for interconnecting two relatively movable bodies, comprising spacedapart attachment means for respective attachment to the two bodies, an elastic element interconnecting the two attachment means to provide damping of relative movement therebetween, and additional damping means associated with the elastic element for providing additional damping against increased movement between the attached means.

According to the invention, there is also provided a vibration-damping unit for connection between two relatively vibratable bodies, comprising a first rigid attachment for connection to one of the bodies, a second 2 rigid attachment for connection to the other body, an elastic connecting element extending between the first and second rigid attachment, the elastic element comprising a first shaped block of elastic material embedding the first attachment, a second shaped block of elastic material embedding the second attachment, relatively flexible elastic material integrally interconnecting the two blocks of elastic material and defining a free space, tension-resistant means positioned around the elastic element to resist tensile forces acting between the two rigid attachments, and compression- resistant means mounted within the free space for resisting compression forces acting between two rigid attachments.

Vibration-damping links embodying the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a plan view of one of the links; Figure 2 is a section on the line II-II of Figure 1 Figure 3 is a perspective view of the underside of the link of Figure 1; Figure 4 is a graph for explaining the operation of the 3 link of Figures 1,2 and 3; Figure 5 is a plan elevation of another of the links; Figure 6 shows detail of part of the link of Figure 5; Figure 7 is a view corresponding to Figure 5 and showing a modified form of the link of that Figure; and Figure 8 is a view corresponding to Figure 7 and showing a modified form of the link of that Figure.

The link 10 shown in Figures 1 and 2 is for interconnection between two relatively movable bodies, such as the engine of a motor vehicle and the vehicle body. For example, the link 10 may be used to support the engine in a pendular fashion. The link comprises two rigid metal tubes 12,14. Strong metal pins connected to the engine and body pass through these tubes in use so that the link is connected between them in a supportive manner and is subjected to vibratory and other movement of the engine relative to the vehicle body.

Each of the tubes 12,14 is embedded in a respective bushing 16,18 of an elastic element 20 which extends between the two ends of the link. The elastic element may 4 be made of stiff rubber, for example. The element 20 is confined within a band 22 of metal or plastic or other suitable material. The enlarged ends 16,18 of the element 20 are connected by integral flexible walls 23 and 24 having a free space 25 between them which is positioned a rigid element 26. The element 26 is supported by a cross-over frame 28 which is integrally connected to the band 22 (see Figure 3) and comprises cross- over arms 30 and 32. The arms 30 and 32 support the element 26 suspended within the free space 25.

In use, the rigid band 22 resists tensile forces acting through the elastic element 20 between the tubes 12 and 14 - that is, forces caused by vibration of the engine and tending to move the tubes 12,14 apart. Compressive forces acting on the element 20, tending to move the bushings 16,18 towards each other, are limited by eventual abutment between the bushings 16,18 and the respective ends of the rigid element 26.

At low amplitudes of vibration (when the engine is stopped or running very slowly, for example) the link 10 has relatively low stiffness, the stiffness being constituted almost entirely by the stiffness of the elastic element 20. In other words, the link operates in region I of the curve shown in Figure 4, in which displacement is plotted along the horizontal axis and resistive force along the vertical axis.

However, as the amplitude of the vibrations of the engine increase, the stiffness of the link will be increased because the effect of the elastic member 20, in resisting vibrations, will be augmented by the effects of the metal band 22 and the stiff central element 26. The link is now operating within the region II of the curve shown in Figure 4.

As shown in Figure 2, the elastic element 20 is provided at each of its ends with a lip 33 which secures it within the band 22.

In the link 34 shown in Figures 5 and 6, parts corresponding to those in Figures 1,2 and 3 are similarly referenced.

The link 34 of Figures 5 and 6 differs from the link of Figures 1,2 and 3 in that the stiff central element 26 of the link 10 is replaced, in the link 34, by a damping unit 35. The damping unit is of the hydroelastic type and comprises an elastic walled chamber 36 which is in abutment with the lower end of the bushing 16. The chamber 36 is supported in a stiff frame 38 which is 6 integral with the band 22. The frame 38 carries a subsidiary elastic walled chamber 40 which is in hydraulic communication with the chamber 36 through a control unit 42 which incorporates a channel connecting the chambers 36 and 40 via a restricted passageway, the characteristics of the channel and the restricted passageway being designed to produce required damping characteristics. As shown in the more detailed view of Figure 6, the control unit 42 may incorporate an elastomeric membrane 44.

The elastic walled chambers 36 and 40 may be produced by blow-moulding from a thermoplastic elastomer.

In operation, damping at low amplitudes of vibration is provided almost entirely by the elastic element 20 (as in the link of Figures 1,2 and 3) and the stiffness is relatively low. AS the vibrations increase, however, additional damping is provided by the hydroelastic damping unit 35. Initially, the damping unit 35 absorbs such vibrations by oscillation of the membrane 44. As the vibrations continue to increase, however, fluid is forced between chambers 36 and 40 via the restricted passageway mentioned above, thus providing further damping. Vibration of the bushing 16 is limited by the stop 37. It will be noted that the damping unit 35 acts between the bushing 16 and the stiff frame 38 in the link of Figure 5.

7 Figure 7 shows a modified arrangement of the link of Figures 5 and 6 and, again, parts in Figure 7 corresponding to those in the other Figures are similarly referenced.

The link 46 of Figure 7 differs from the link 34 of Figures 5 and 6 in that the hydroelastic damping unit 35 of Figures 5 and 6 is replaced by a hydraulic damping element 48. As shown, this comprises a piston 50 connected via a piston rod 52 to the bushing 16, the piston sealingly sliding in a cylinder 54 which is mounted on the rigid frame 38. The cylinder is filled with hydraulic fluid, and the piston has one or more through passageways 56 enabling the fluid to pass from one side of the piston to the other as it moves within the cylinder, the amount of damping produced being dependent on the cross-sectional size of the passageways 56.

Again, the operation is generally as already described. At low levels of vibration, damping is provided almost entirely by the elastic element 20 with relatively low stiffness. As the vibration amplitude increases, however, additional damping is provided by the hydraulic damper 48. Again, the hydraulic damper 48 acts between the bushing 16 and the stiff frame 38.

8 Figure 8 shows a modification to the link of Figure 7. In the link of Figure 8, the hydraulic damper 48 does not act between the bushing 16 and the stiff frame 38 of Figure 7 but instead acts between the two bushings 16,18. Such an arrangement gives modified characteristics to the link. In the link of Figure 8, the damping effect of the hydraulic damper 48 does not come into operation until one or other of the bushings 16,18 has come into contact with the respective stop 37,49.

In a further modification, the link of Figure 8 may use a damping unit 35 (Figure 5) instead of the hydraulic damper 48.

The links described are advantageous because they provide controllably variable damping characteristics. They thus contrast with other types of link having rubber bushes at each end (for connection to the engine and the chassis respectively), the rubber bushes being supported within respective metal tubes which are rigidly interconnected. In such other arrangements, damping is produced only by the stiffness of the rubber bushes and cannot be effectively controlled or varied. Furthermore, the space between the bushes at each end of the link is occupied solely by the rigid metal interconnection and is not performing any useful purposes. In the links described 9 and illustrated, however, the design is such that the part of the link intermediate its two ends is used in a functionally advantageous way to enable the vibration-damping characteristics of the link to be controllably varied.

Claims

1. A vibration-damping link for interconnecting two relatively movable bodies, comprising spaced-apart attachment means for respective attachment to the two bodies, an elastic element interconnecting the two attachment means to provide damping of relative movement therebetween, and additional damping means associated with the elastic element for providing additional damping against increased movement between the attachment means.

2. A link according to claim 1, in which the additional means comprises relatively tension-resistant means interconnecting the two ends of the elastic element to provide a tensile force resisting their movement apart.

3. A link according to claim 2, in which the tension-resistant means comprises a stiff band within whose periphery is mounted the elastic element.

4. A link according to any preceding claim, in which the additional means comprises relatively stiff compression-resistant means mounted between the two ends of the elastic element in such a position as to resist a compressive force applied to it by the moving together of the two ends.

5. A link according to claim 4, in which the elastic means comprises elastic wall means extending between and interconnecting the two ends of the elastic element and defining a free space. and in which the compression-resistant means comprises a rigid member mounted within the free space.

6. A link according to claim 4, in which the elastic element comprises elastic wall means extending between and interconnecting the two ends of the element and defining a free space, and in which the compress ionresistant means comprises a hydroelastic damping unit mounted within the free space.

7. A link according to claim 4, in which the elastic element comprises elastic wall means extending between between and interconnecting the two ends of the element and defining a free space. and in which the compress ion-resi stant means comprises a hydraulic damping unit mounted within the free space.

8. A link according to claim 6 or 7, in which the compression- res i stant means acts between the two ends of the elastic element.

9. A link according to claim 6 or 7, in which the 12 compression-resistant means acts between one of the two ends of the elastic element and a rigid member.

10. A vibration-damping unit for connection between two relatively vibratable bodies, comprising: a first rigid attachment for connection to one of the bodies, a second rigid attachment for connection to the other body; an elastic connecting element extending between the first and second rigid attachments; the elastic element comprising a first shaped block of elastic material embedding the first attachment, a second shaped block of elastic material embedding the second attachment, and relatively flexible elastic material integrally interconnecting the two blocks of elastic material and defining a free space; tension-resistant means positioned around the elastic element to resist tensile forces acting between the two rigid attachments; and compression- res i st ant means mounted within the free space for resisting compression forces acting between two rigid attachments.

11. A link according to claim 10, in which the tension-resistant means comprises a relatively rigid band surrounding the elastic element.

12. A link according to claim 10 or 11, in which the compressionresistant means comprises a relatively rigid 13 member mounted within the free space.

13. A link according to both claims 11 and 12, in which the rigid member is mechanically connected to the said band.

14. A link according to any one of claims 10 to 12, in which the compression-resistant means comprises a hydro-elastic damping element mounted within the free space.

15. A link according to any one of claims 10 to 12, in which the compression-resistant means comprises a hydraulic damping element mounted within the said free space.

16. A vibration-damping link, substantially as described with reference to Figures 1,2 and 3 of the accompanying drawings.

17. A vibration-damping link, substantially as described with reference to Figures 5 and 6 of the accompanying drawings.

18. A vibration-damping link, substantially as described with reference to Figure 7 of the accompanying drawings.

14

19. A vibration-damping link, substantially as described with reference to Figure 8 of the accompanying drawings.